The nuclear coiuponents of the sex cells of four species of cockroaches. 513 
and is to be compared with III, b. Therefore, althougb there are 
rumor and unimportant differences between this description and that 
given for Periplaneta , the essential features are identical. It ruay 
be remarked that it is an assumption on the part of the Scandinavian 
writers that a reductional division occurs, for here, as in the case 
of Periplaneta , a fusion of the chromosomes seems to occur immediately 
after synapsis, as in III, c, so that identification of the longitudinal 
split which is represented by the space within the ring (VI, c), cannot 
be rnade surely. 
As Gregoire and Deton (’Oö) and others have shown, there is 
no essential difference between telosynapsis and parasynapsis and in 
the cases considered in the present instance, it will be observed that 
the end results are the same in essential respects. 
e) The odd chromosome and the plasmosome. Moore and Ro- 
binson (’04) nowhere distinguish between the odd chromosome and 
the plasmosome, as will be seen from the quotation given on p. 2 
and from the following, which describes the contraction phases; — 
"As the loops of chromatin contract, the nucleolus also becomes shorter 
and thicker, the extremity remote from the archoplasm assuming the 
appearance of a dense blot on the surface of the nucleus. Düring 
this latter phase, the long, attenuated tail of the nucleolus is retracted 
and the nucleolus assumes a spherical form and apparently lies 
suspended in the nuclear sap among the skein-like mass of chroma- 
tin bands. It remains quiescent in this condition, throughout the 
following heterotype prophases until the chromatin loops again con- 
tract towards the nuclear membrane at the point adjacent to the 
archoplasm. The nucleolus then undergoes fragmentation, gives rise 
to a number of small, highly refractive chromatic bodies, lying 
entangled in the bunch of contracted loops.” 
As state<| above, the writer has clearly distinguished two com- 
ponents in this "dense blot”, one being chromatic (the odd chromo- 
some) and the other being a plastin body (the plasmosome) Foot 
and Strobell (’07) and more recently G. Arnold (’08) have taken 
the stand that no odd chromosome is present in the forms they have 
studied, Anasa tristis and Hydrophilus piceus, respectively, but that 
either error in counting or confusion with plastin bodies has been 
responsible for the conclusion that such a chromosome is present. 
With regard to the first instance, where a specific case was made 
against the work of Wilson (’05 a and b) and Montgojiery (’06) on 
Anasa tristis, Lekevre and Mc Gill (’08) have fully corroborated 
34 * 
